This invention relates to copy sheet feed apparatus in an electrophotographic copying machine which feeds copy substrates to the print forming section of the photosensitive drum or belt in the copying machine.
Heretofore, this type of mechanism consisted of intermittently rotating rollers whose speed equalled the photosensitive drum surface speed, (hereinafter referred to as the process speed) or a cam type mechanism, which fed the copy substrate or transfer material on a signal from the copying process to synchronize it with the movement of the print-forming section of the photosensitive drum. For this type of mechanism it is difficult to minimize the error in matching the positions of the leading edge of the copy sheet to the print forming section of the photoreceptor below the allowable tolerance of about 2 mm. This is because it is impossible to perfectly synchronize the movement of the print-forming section of the photosensitive drum with the intermittent drive of the rollers due to the time difference between receipt of the signal and the rollers intermittent driving of the transfer material, the faster the rollers rotate the greater the error in adjusting the position of the leading edge of the transfer material to the print-forming section becomes as a result. Conversely, the slower the rotational speed the smaller the aforementioned positional error becomes. It is therefore desirable that the rollers rotate as slowly as possible. However, it becomes difficult to adjust the transfer material to the print-forming section on the photosensitive drum by only causing the rollers to revolve more slowly. This is due to the fact that the transfer material feed velocity must equal the process speed in order to adjust the transfer material to the print-forming section of the photosensitive drum.
Accordingly, it is an object of the present invention to reduce the positional error between a leading edge of the copy substrates and an image on a photoreceptor.
Yet another object of the present invention is to diminish positional error between an image on a photoreceptor and a copy sheet by adjusting the feed velocity of the copy sheet to the photoreceptor velocity.
The foregoing and other objects of the present invention are accomplished by driving the transfer material toward the photoreceptor with primary rollers revolving at a speed less than the speed of the photoreceptor toward a nip formed by secondary rollers which are rotating at a speed equal to the photoreceptor speed. As the transfer material reaches the nip of the secondary rollers and is gripped thereby the primary rollers stop their driving force and allow the transfer material to be synchronously driven by the secondary rollers at the same speed as the photoreceptor in order for an image to be transferred from the photoreceptor to the transfer material.